Moisture and carbon dioxide management system in electrochemical cells

ABSTRACT

An electrochemical cell utilizes an air flow device that draws air through the cell from a scrubber that may be removed while the system is operating. The negative pressure generated by the air flow device allows ambient air to enter the cell housing when the scrubber is removed, thereby enabling continued operation without the scrubber. A moisture management system passes outflow air from the cell through a humidity exchange module that transfers moisture to the air inflow, thereby increasing the humidity of the air inflow. A recirculation feature comprising a valve allow a controller to recirculate at least a portion of the outflow air back into the inflow air. The system may comprise an inflow bypass conduit and valve that allows the humidified inflow air to pass into the cell inlet without passing through the scrubber. The scrubber may contain reversible or irreversible scrubber media.

CROSS REFERENCE TO RELATED APPLICATION

This patent application claims priority to provisional patentapplication 62/365,866 filed on Jul. 22, 2016, which is incorporated byreference herein in its entirety.

BACKGROUND Field

The present disclosure is directed to moisture and carbon dioxidemanagement systems for electrochemical cells, and more in particular, toelectrochemical cells comprising air breathing cathodes and utilizing aliquid ionically conductive medium.

Background

Many types of electrochemical cells utilize a liquid ionicallyconductive medium to support electrochemical reactions within the cell.Electrochemical cells may utilize an air breathing electrode coupled toa fuel electrode, comprising any suitable fuel. For example, a metal-airelectrochemical cell system may comprise a plurality of cells, eachhaving a fuel electrode serving as an anode at which metal fuel isoxidized, and an air breathing oxidant reduction electrode at whichoxygen from ambient air is reduced. The liquid ionically conductivemedium in such cells may communicate the oxidized/reduced ions betweenthe electrodes.

In various ionically conductive mediums, evaporation, electrolysis (e.g.water splitting on recharge or during self-discharge) or other loss ofmoisture from the ionically conductive medium, may be detrimental to theelectrochemical cell, particularly for cells requiring water to operate.For example, salting of the ionically conductive medium due to waterloss, may clog an oxidant electrode of the electrochemical cell,reducing its performance or, in extreme cases, resulting in completecell failure. Such salting or other failures may occur, for example,where an air-side of the oxidant electrode, or a portion thereof, isexcessively dry. Additionally, a decrease in water content in theionically conductive medium may decrease the medium's solvatingcapacity, i.e., its ability to dissolve solutes, or increase thepercentage concentration of solutes in the medium, affecting thefunctionality of the ironically conductive medium.

Metal-air electrochemical cells are utilized in a wide variety ofenvironmental conditions, including very hot and dry environments. Thesecells may have limited effectiveness and/or life as a result of the lossof moisture from the liquid ionically conductive medium.

Electrochemical cell water conservation and management systems have beendeveloped such as U.S. patent application Ser. No. 14/176,888, filedFeb. 10, 2014, Fluidic Inc., which provides an example of a batterywater management system; the entirety of which is hereby incorporated byreference in its entirety.

SUMMARY

The disclosure is directed to an electrochemical cell, such as ametal-air electrochemical cell that can effectively operate in a widerange of environmental conditions, including very arid environments.Many electrochemical reactions benefit from an oxygen rich air supply oran airflow with reduced carbon dioxide. In addition, in alkaline fuelcells or rechargeable battery systems comprising an alkalineelectrolyte, carbon dioxide can react with the electrolyte to formpotassium carbonate, which lowers the conductivity of the electrolyte bydecreasing the hydroxide concentration and decreasing the solubility ofa metal species, such as zinc. In addition, precipitation of carbonatewithin the pores of the air electrode can damage the electrode, expandthe pore structure and lead to leakage. It is to be understood that someembodiments of the moisture, i.e. water, and carbon dioxide managementsystem described herein, may be utilized in various electrochemicalcells, including fuel cells and in particular, alkaline fuel cells andpolymer electrolyte membrane (PEM) fuel cells. In alkalineelectrochemical cells, such as metal-air batteries, that use airbreathing electrodes which have open communication to air at ambientconditions, carbon dioxide is absorbed from the air into the electrolytethrough the air breathing electrode, and moisture (water) is lost fromthe electrolyte to the air (ambient) through evaporation through the airbreathing electrode. This disclosure utilizes multiple mechanisms and/ormethods, e.g., four, to decrease the amount of carbon dioxide absorbedfrom the air and moisture lost to the air, e.g., in accordance with oneembodiment: a carbon dioxide scrubber to remove carbon dioxide from theair prior to it entering the air breathing electrode chamber; a humidityexchange membrane (HEM) which transfers moisture lost throughevaporation into the air stream leaving the air breathing electrodechamber back into the air stream entering the air breathing electrodechamber; an air recirculation mechanism that directs a portion of carbondioxide depleted, humidity laden air leaving the air breathing electrodechamber back into the air stream entering the air breathing electrodechamber; and a vent filter that catches and returns electrolyte liquiddroplets leaving the cell as a mist due to gas generated during normalcell electrochemical reactions and returning that liquid back to thecell. These mechanisms may operate independently or dependently toreduce the amount of carbon dioxide absorbed into the electrolyte and toreduce the amount of moisture lost from the cell.

The summary of the disclosure is provided as a general introduction tosome of the embodiments of the disclosure, and is not intended to belimiting. Additional example embodiments including variations andalternative configurations of the disclosure are provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure,and together with the description serve to explain the principles of thedisclosure.

FIG. 1 depicts a schematic view of an electrochemical cell having animmersed oxidant reduction electrode.

FIG. 2 depicts a schematic view of an electrochemical cell having anoxidant reduction electrode which defines a boundary wall for theelectrochemical cell.

FIG. 3 shows a side perspective view of an exemplary electrochemicalcell having a scrubber module that is detached from the cell housing.

FIG. 4 shows a side view of an exemplary electrochemical cell having ascrubber module that is removed and a bypass adapter configured from theinflow port to the outflow port.

FIG. 5 shows a side view of an exemplary electrochemical cell having ascrubber module that is attached to the cell housing.

FIG. 6 shows a top view of an exemplary electrochemical cell having amoisture management system comprising a recirculation valve andscrubber.

FIG. 7 shows a top perspective view of an exemplary electrochemical cellhaving a moisture management system.

FIG. 8 shows a top perspective view of an exemplary electrochemical cellhaving a control system.

FIG. 9 shows an exemplary outflow bypass conduit within the manifoldportion of the electrochemical cell.

FIG. 10 shows an exploded view of an exemplary scrubber having a heatingelement.

FIG. 11 shows a cross-sectional schematic of an exemplaryelectrochemical cell having a moisture and carbon dioxide managementsystem.

FIG. 12 shows a block diagram of a water management system.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Corresponding reference characters indicate corresponding partsthroughout the several views of the figures. The figures represent anillustration of some of the embodiments of the present disclosure andare not to be construed as limiting the scope of the disclosure in anymanner. Further, the figures are not necessarily to scale, some featuresmay be exaggerated to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Also, use of “a” or “an” are employed to describeelements and components described herein. This is done merely forconvenience and to give a general sense of the scope of the disclosure.This description should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

Certain exemplary embodiments of the present disclosure are describedherein and are illustrated in the accompanying figures. The embodimentsdescribed are only for purposes of illustrating the present disclosureand should not be interpreted as limiting the scope of the disclosure.Other embodiments of the disclosure, and certain modifications,combinations and improvements of the described embodiments, will occurto those skilled in the art and all such alternate embodiments,combinations, modifications, improvements are within the scope of thepresent disclosure.

An exemplary moisture and carbon dioxide system in accordance withembodiments of this disclosure may comprise a recirculation mechanismwherein at least a portion of the air exiting the electrochemical cellis recirculated back into the air inflow to the cell. Manyelectrochemical cells produce heat and an exhaust flow that is high inhumidity and therefore conserving this moisture through recirculationcan effectively conserve the moisture in the system.

An exemplary moisture and carbon dioxide management system in accordancewith embodiments of this disclosure comprises a humidity exchangemembrane (HEM), for transfer of moisture from the outflow of air from achamber containing the air breathing electrode of the electrochemicalcell to the air inflow of said chamber. The HEM comprises a moistureexchange material, such as a membrane comprising an ionomer, such asperfluorosulfonic acid polymer, for example. A HEM separates air inflowto the cell from air exiting the electrochemical cell, such as from theoxidant reduction electrode air chamber, whereby moisture from the airexiting the cell is transferred through the humidity exchange membraneto the air inflow due to a relative humidity (RH) difference across themembrane (air oufflow at high RH, air inflow at low RH). The air exitingthe oxidant reduction electrode air chamber, or air chamber outflow, iswarm and humid and therefore can carry a relatively high amount ofmoisture which enables the HEM to work effectively. This exiting airpicks up moisture from the liquid ionically conductive medium as itflows through the cell and is heated due to the increased heat from thechemical reactions. The air chamber outflow may be hotter and contain arelatively high moisture content. For example, the air chamber outflowmay be 10° C., 20° C., 30° C., or 40° C. hotter than the air inflow. Theelectrochemical reactions within the cell heat the air chamber and alsohumidify the air chamber air. For example, the air chamber oufflow mayhave a relative humidity of more than about 70%, more than about 80%,more than about 90%, more than about 95%, and substantially fullysaturated, depending on the flow rates, size of the system andenvironmental conditions. As an example, air inflow may be very dry, atonly 20% relative humidity at 30° C. and may pass by a HEM module havingair chamber outflow on the opposing side of the HEM at 90% relativehumidity at 50° C., to increase the air inflow humidity to about 70%before entering the cell. A HEM may be configured in a module comprisingmultiple layers, folds, pleats or corrugations of the HEM to increasethe amount of surface area that the air stream must flow over, therebyincrease the amount of moisture transferred. In accordance with anembodiment, a marketed or manufactured HEM or HEM module may be used. Anexemplary HEM or HEM module is available from DPoint Technologies,Vancouver, BC, Canada, for example, and may be used in the disclosedsystem. However, this example is not intended to be limiting.

An exemplary moisture and carbon dioxide management system in accordancewith embodiments of this disclosure comprises a recirculation feature,such as a valve or other mechanism, that may be configured toreintroduce some of the air chamber outflow directly back into the airinflow, thereby increasing the moisture level of the air inflow. When anelectrochemical cell is located in a very arid environment,recirculation of the outflow air into the air inflow can effectivelyconserve moisture in the system. A recirculation feature may beconfigured upstream, prior to the inflow air reaching the HEM, ordownstream of the HEM. In one embodiment, it may be preferred to locatea recirculation feature upstream of the HEM, whereby the outflow airflows past the HEM, thereby maintaining the HEM in a warm moist state,prior to recirculation. As described herein, in some embodiments, a HEMmay work more effectively when maintained in a warm and moist condition.A recirculation feature may be a valve that is operated by a controlsystem or may be a baffle that is automatically controlled by pressure.A control system may monitor the moisture level within and external tothe system, such as relative humidity, RH, of the air inflow, the airoutflow, the ambient RH, the liquid electrolyte level and the like todetermine when and how much recirculation to include into the airinflow. The air exiting the oxidant reduction electrode air chamber, orair chamber outflow, is warm and humid and a portion or amount thereofmay be recirculated into the air inflow. In one embodiment, a valve isopened and closed to control when the air chamber outflow isrecirculated and what portion or amount is recirculated. For example, invery arid environments, a high proportion of the air chamber outflow maybe recirculated, such as about 40% or more, about 50% or more, about 70%or more, about 90% or more, or all of the air chamber outflow or anyportion between and including the percentages provided. The remainingair chamber outflow may be passed through the air flow device and out ofthe cell.

For example, in one embodiment, an exemplary electrochemical cell mayutilize a recirculation feature that provides about 50% of the inflow tothe cell from air outflow from the cell. The ambient air, or inlet airmay comprise about 400 ppm carbon dioxide, 50% RH, and 21.2% oxygen. Theair outflow from the cell may have a reduced carbon dioxideconcentration, such as about 0%, due to the scrubber and/or reactionwithin the cell, 100% RH, and a reduced oxygen concentration of about12%. When the ambient air and air outflow from the cell are mixedthrough the recirculation feature the inlet airflow to the cell willhave a 200 ppm carbon dioxide concentration, about 75% RH, and 18%oxygen. The electrochemical cell may be configured to run at a three orfour stoichiometry for oxygen and therefore a slightly reduced oxygenconcentration will not create a loss of power generation potential. Inaddition, there will be a large benefit from the increase humidity leveland reduced carbon dioxide level which will result in extending the lifeof the electrochemical cell.

An exemplary moisture and carbon dioxide management system in accordancewith embodiments of this disclosure comprises a mist elimination systemthat may be incorporated to control the loss of liquid ionicallyconductive medium, such as an electrolyte. A mist elimination system maycomprise a baffle or valve, a filter, a hydrogen recombination catalyst,a neutralizer and a hydrophobic filter. An exemplary mist eliminationsystem reacts hydrogen to form water that may be drained back into theelectrochemical cell. Gasses produced during normal cell operation, suchas for a metal-air cell during self-discharge or cell charge, rise tothe surface of the electrolyte as bubbles which burst at the electrolytesurface. The action of the bursting bubble generates a fine mist ofelectrolyte which will leave the cell with the effluent gas stream. Anexemplary mist elimination filter is placed in this gas stream torecapture this electrolyte mist and return it to the liquid electrolyte.

The operational relative humidity ranges, or humidity ranges within theair chamber, may depend on the particular ionically conductive medium,in addition to the temperature of ambient air and the cell, for example.It may be appreciated that aqueous salt electrolytes, e.g., potassiumhydroxide, may be characterized as hygroscopic. For example, for a cellcomprising an aqueous KOH electrolyte, a relative humidity less than ca.50% may result in water loss through the oxidant reduction electrode, orair electrode. An ambient relative humidity greater than 80% (or greaterthan ca. 80%) may result in water uptake into the cell through theoxidant reduction electrode, or air electrode. Water release through theair electrode may occur at greater relative humidity than ca. 50% in anair temperature range of 50 degrees Celsius to 80 degrees Celsius. Arelative humidity from 50% (inclusive) to 80% (inclusive), or in amid-range, may be characterized as neutral. For example, at 70%relatively humidity into the cell, 250 ml of water may be lost at 50degrees C., and only 15 ml (which is considered negligible in a cellhaving 8 liters total volume) is lost at 25 degrees C. It should beappreciated that the ranges may also and/or alternatively changedepending on the ionically conductive medium and itshygroscopic/hygrophobic characteristics.

A variety of water management techniques are described herein and may beused with the disclosed system. U.S. patent application Ser. No.15/077,341, to Fluidic Inc., filed on Mar. 22, 2016, entitled WaterManagement System In Electrochemical Cells with Vapor Return ComprisingAir Electrodes describes some other water management systems andtechniques and is incorporated, in its entirety, by reference herein.

An exemplary moisture and carbon dioxide management system in accordancewith embodiments of this disclosure comprises a scrubber module forremoving carbon dioxide, CO₂, from the air inflow to the cell. Someexemplary scrubber media, such as soda-lime, requires some moisture toreact with the carbon dioxide. The scrubber media may absorb somemoisture from the air inflow. This absorbed moisture may be reintroducedto the cell by heating of the scrubber. Heating may be passive heating,wherein heat generated from the cell is used to heat the scrubber, or adedicated resistive heater element may be used to heat the scrubber.

An exemplary scrubber system operates more effectively when the incomingair to the scrubber is humidified and therefore receiving inflow air tothe scrubber after passing through the HEM may improve overall systemeffectiveness. The scrubber may absorb some of the moisture from theairflow therethrough, and this absorbed moisture may be reintroduced tothe cell by heating the scrubber. Heating may be passive heating,wherein heat generated from the cell is used to heat the scrubber, or adedicated resistive heater element, controlled by the controller, may beused to heat the scrubber. In the case of passive heating, heat from theelectrochemical cell may be conducted to the scrubber module andspecifically to the scrubber media. Conductive elements may beconfigured to increase the amount of heating that his conducted to thescrubber media. In the case of active heating, an electrically resistiveheating element is configured to heat the scrubber and/or scrubbermedia. Electrical current generated by the electrochemical cell may bepassed through the electrically resistive heating element continuouslyor it may be turned on and off by a switch that is activated by thecontrol system. Again, the control system may receive input values fromone or more sensors that are used to activate the heating of thescrubber heater. In an exemplary embodiment, the electrochemical cellmay be configured to run the airflow device even when theelectrochemical cell is not operating to produce power, and therebyabsorb moisture from the environment in the scrubber media which may besubsequently desorbed, or driven out of the scrubber media and into theelectrochemical cell. For example, the control system may subsequentlyheat the scrubber media to drive off absorbed moisture from the scrubbermedia.

An exemplary scrubber comprises scrubber media that is reversible orirreversible. A reversible scrubber media may be reactivated by heating,for example, wherein the absorbed carbon dioxide is desorbed and drivenoff from the scrubber media. A reversible scrubber material may bereactivated by heating to about 70° C. or more, or about 90° C. or more.Therefore, a scrubber module that is configured to be heated to driveoff absorbed moisture may also be reactivated when comprising areversible scrubber media. When irreversible scrubber media reacts withthe carbon dioxide it is changed chemically and is consumed. Scrubbermedia, irreversible or reversible, may be purged periodically toregulate the humidity level and in the case of reversible media, todrive off the absorbed carbon dioxide. A purge cycle may be run while areversible scrubber media is heated to more effectively purge thedesorbed carbon dioxide from the system. During a scrubber purge cycle,a flow of air through the scrubber may be reversed, wherein the air flowdevice, such as a fan, is reversed and therefore pushes air through thecell into the scrubber and out of the air inlet. In addition, the rateof flow of air through the scrubber may be increased, wherein the flowrate is higher, such as at least two times, three times, five times, tentimes or more higher than a standard operational flow rate. This may beaccomplished by increasing the fan speed, for example. In still anotherembodiment, a valve enables air to flow through the scrubber and thendirectly out of the outlet of the system without passing through thecell housing, and/or without passing by the HEM after it exits thescrubber.

A scrubber media may comprise media or material(s) selected from thegroup of: soda lime, sodium hydroxide, potassium hydroxide, and lithiumhydroxide, lithium peroxide, calcium oxide, serpentinite, magnesiumsilicate, magnesium hydroxide, olivine, molecular sieves, amines, andmonoethanolamine, and/or derivatives and/or combinations thereof. Aminescrubber media is reversible whereas soda lime is irreversible.

A scrubber configured to remove carbon dioxide from an air inflow to ametal-air electrochemical cell is described in U.S. patent applicationSer. No. 15/077,341, to Fluidic Inc., filed on Mar. 22, 2016, entitledWater Management System In Electrochemical Cells with Vapor ReturnComprising Air Electrodes and currently pending; the entirety of whichis hereby incorporated by reference herein.

Various portions of the electrochemical cell 100 may be of any suitablestructure or composition, including but not limited to being formed fromplastic, metal, resin, or combinations thereof. Accordingly, the cell100 may be assembled in any manner, including being formed from aplurality of elements, being integrally molded, or so on. In variousembodiments the cell 100 and/or the housing 110 may include elements orarrangements from one or more of U.S. Pat. Nos. 8,168,337, 8,309,259,8,491,763, 8,492,052, 8,659,268, 8,877,391, 8,895,197, 8,906,563,8,911,910, 9,269,996, 9,269,998 and U.S. Patent Application PublicationNos. 20100316935, 20110070506, 20110250512, 20120015264, 20120068667,20120202127, 20120321969, 20130095393, 20130115523, and 20130115525,each of which are incorporated herein in their entireties by reference.

FIG. 1 illustrates a schematic cross sectional view of anelectrochemical cell 100. As shown, the components of theelectrochemical cell 100 may be contained at least partially in anassociated housing 110. The cell 100 utilizes a liquid ionicallyconductive medium 124, such as an electrolyte 126, that is containedwithin the housing 110, and is configured to circulate therein toconduct ions within the cell 100. While at times the ionicallyconductive medium may be generally stationary within the housing 110,such as in a stagnant zone, it may be appreciated that the cell 100 maybe configured to create a convective flow of the ionically conductivemedium. In some embodiments, the flow of the ionically conductive mediummay be a convective flow generated by bubbles of evolved gas in the cell100, such as is described in U.S. patent application Ser. No. 13/532,374incorporated above in its entirety by reference.

Although in the illustrated embodiment of FIG. 1 the cell housing isconfigured such that the oxidant reduction electrode 150 is immersedwith the oxidant reduction electrode module 160 into the cell chamber120, it may be appreciated that in various embodiments, otherconfigurations or arrangements of the cell 100 are also possible. Forexample, in FIG. 2, another embodiment of the cell 100 (specifically,cell 100*) is presented, whereby an oxidant reduction electrode 150*defines a boundary wall for the cell chamber 120, and is sealed to aportion of a housing 110* so as to prevent or substantially preventseepage of ionically conductive medium therebetween. In some cases,however, such a configuration is generally not preferred, however, dueto concerns that a failure of the oxidant reduction electrode 150* wouldresult in leakage of the ionically conductive medium out of the cell100*. Regardless, in some such embodiments the convective flow of theionically conductive medium in the cell chamber 120, described ingreater detail below, may be in a direction upwards and away from theoxidant reduction electrode 150*, across the top of the fuel electrode130.

As shown in FIG. 3, an exemplary electrochemical cell 100 has a scrubbermodule 60 that is detachably attachable to the cell housing 110. Thescrubber module may be detached from the electrochemical cell while theelectrochemical cell is running. Since air is drawn in to the cell by anairflow device, removal of the scrubber module still allows air to enterinto the inflow port 65. This allows for removal of the scrubber modulefor maintenance or replacement without interfering with the operation ofthe electrochemical cell. In normal operation with the scrubberattached, air is drawn in through the air intake 40, into the scrubberthrough the outflow port 61 and into the inlet port of the scrubber 62.The air then exits the scrubber through the outlet port of the scrubber64 and enters back into the cell housing through the inflow port 65. Airpasses from the air inflow port 65 into the air chamber of the oxidantreduction electrode (not shown). A cover 111 is configured over the topof the electrochemical cell housing 110, or over the cell manifoldassembly 114. The cover and manifold assembly help to protect the cellcomponents from the elements and keep dust, rain and other environmentalelements out. An exhaust vent 45 is configured as an outlet for gasventing from the interior chamber of the cell.

As shown in FIG. 4, the scrubber module 60 is detached from theelectrochemical cell 100 and a bypass adapter 77 extends from theoutflow port 61 to the inflow port 65. Incoming airflow passes throughthe outflow port 61, into the outflow port end 79 of the bypass adapter,through the bypass adapter 77, out of the cell inflow end 78 of thebypass adapter and into the inflow port 65. The bypass adapter allowshumid air inflow into the cell, when a HEM is utilized, while thescrubber is removed. The bypass adapter enables the cell to operatewithout the scrubber without any excessive moisture loss. The bypassadapter shown is a physical connector having an auxiliary conduit forpassing inflow air into the inflow port. It is to be understood thatthis bypass flow may be accomplished through an inlet bypass conduit,configured as part of the cell, along with a valve to open flow up to aninlet bypass conduit, as shown in FIG. 12.

As shown in FIG. 5, the scrubber module 60 is attached to the outflowport 61 and inflow port 65 of the manifold assembly 114. The terminalsof the cell 44 are shown extending from the manifold assembly 114.

Referring now to FIGS. 6 to 8, an exemplary electrochemical cell 100 hasa moisture management system 59 comprising a humidity exchange membranemodule 50, recirculation feature 70, such as a valve or baffle, andscrubber 60. Ambient air enters the cell through the air intake 40 andis passed along the inflow side 51 of the HEM where it picks up moisturefrom the air flowing along the outflow side 52 of the HEM. The air thenflows through the outflow port 61 and into the scrubber module 60through the inlet port of the scrubber. The air then flows through thescrubber media, wherein carbon dioxide is removed from the airflow. Theair then flows back into the cell housing 110 and into the cathode inlet41, and subsequently into the oxidant reduction electrode air chamber.The air flows through the air chamber and out of the air chamber outlet42, or cathode outlet, which is on an opposing end of the cell housingfrom the cathode inlet. The air then flows through an outflow bypassconduit that extends along the bottom of the manifold assembly 114. Airflows into the bypass inlet 47, through the outflow bypass conduit (notshown), and out of the bypass outlet 49. The airflow then flows over theoutflow side 52 of the HEM. Some of the airflow may be diverted througha recirculation valve 70 back into the air inflow. The remainder of theair is drawn through the airflow device 56 and out of the cell housing.The cell terminals 44 are shown extending from the top of the cellhousing 110. A plurality of sensor leads 46 are shown extending from thetop of the electrochemical cell 100. As described herein, the sensorleads may measure the level of the electrolyte, and/or the humiditylevel of the air chamber. A control system 102, as shown in FIG. 8 mayreceive input from the sensor leads and open, close or adjust the amountof flow through the recirculation feature, or valve. The control systemmay change the amount of flow being drawn into the system and may drawair through the system even when the cell is not operating to producepower. The moisture in the air being drawn through the scrubber may beabsorbed by the scrubber media and retained for later use, wherein thescrubber is heated either passively or actively by the system. Theexemplary control system shown in FIG. 8 comprises a control circuit 104and a microprocessor 106. The control system is configured on top of themanifold assembly 114 and a cover 111, as shown in FIG. 5, extends overthe control system 102.

As shown in FIG. 9, the outflow bypass conduit 48 extends under themanifold assembly 114. Air exiting the air chamber is diverted into thebypass inlet 47 and flows through the conduit to the bypass outlet 49.The air then flows into the HEM 50 or a portion is diverted into theinflow air through the recirculation feature. The air chamber extendsacross a portion of the length of the cell housing.

As shown in FIG. 10, a scrubber module 60 may comprise a heating element69 that is configured to be coupled with the control system to heat thescrubber media 66. The scrubber media as shown is a reversible scrubbermedia 67, a scrubber media that absorbs carbon dioxide that may bedriven off by increasing the temperature of the reversible scrubbermedia. The heating element 69 extends within the scrubber module housing68 to provide effective heating of the scrubber media, but may beconfigured on an exterior surface of the housing. A heater connectorenables the heating element to be easily coupled with the control systemwhen the scrubber module is attached to the cell housing. The controlsystem may turn on the heating elements and control the valves withinthe electrochemical cell to control flow through the scrubber whilebeing heated to effectively remove the carbon dioxide from the scrubbermedia.

As shown in FIG. 11, air flows into the manifold assembly 114 of theelectrochemical cell 100, through the scrubber 60 and then into the airchamber 170. As shown, air enters the air chamber 170 configured withinthe interior chamber 122 of the cell housing 110. The air flows acrossthe air chamber and exits the interior chamber where it enters theoutflow bypass conduit 48. A pressure relief valve 94 is configured tovent pressure from within the cell chamber 120 when exceeding athreshold limit. Also shown in FIG. 11 is a mist elimination system 80that is configured to reduce and/or eliminate mist that evolves from thesurface of the electrolyte due to bubbling of gasses to the surface andto prevent or substantially prevent leakage of the electrolyte 126 inthe event of an upset. The mist eliminator system comprises a safetyvent 82 that is in communication with the interior chamber 122 of thecell housing 110, and therefore exposed to the ionically conductivemedium 124 and/or gas space there above. An exemplary safety ventprovides a tortuous conduit path that will slow the transfer of anyliquid electrolyte to the downstream portions of the mist eliminatorsystem. Another exemplary safety vent comprises a ball valve that allowsair to go around the ball due to a pressure differential when upright,and when upset, seals when the ionically conductive media liquid forcesthe ball against a seat to prevent or substantially prevent liquid loss.A filter 84 is configured downstream of the safety vent and may be aconcave filter that will drain absorbed ionically conductive medium backinto the anode chamber, as described in U.S. Pat. No. 9,269,998,incorporated by reference herein.

The exemplary mist elimination system 80 comprises a hydrogenrecombination portion 86, comprising a hydrogen recombination catalystthat reacts with any hydrogen to form water. The catalyst may beconfigured on a support material such as particles or surfaces of themist elimination system that are exposed to the gas exiting the cellhousing from the anode space. Air may enter in to the mist eliminationsystem through the hydrophobic filter 98 to provide the necessary oxygenfor the hydrogen recombination reaction. The hydrophobic filter mayprevent or substantially prevent water ingress into the electrochemicalcell.

The exemplary mist elimination system comprises a neutralizer portion 90comprising a neutralizer media 91, such as an acid, configured toneutralize the ionically conductive medium. For example, the ionicallyconductive medium may comprise a potassium hydroxide solution that iscaustic, and a neutralizer may be a solid acid or acid on carbon or someother support material. The neutralizer is configured to reduce anyreactive gases that may exhaust from the anode chamber or the chambercontaining the ionically conductive medium.

FIG. 12 shows a block diagram of an exemplary moisture (water)management system 59, and a carbon dioxide management system 13. The twosystems may work in tandem to conserve moisture and provide a carbondioxide depleted inflow stream to the electrochemical cell. The moisturemanagement system increases the humidity of inflow air by drawingmoisture from the outflow exhaust of the cell, which is typically warmand humid, when the cell is operating. The HEM module 50 has an inflowside 51 and an outflow side 52 separated by a HEM 54. The moisture leveland carbon dioxide level of inflow air may further be adjusted byrecirculating at least a portion of the outflow through a recirculationfeature 70, such as a valve or baffle. As shown, the recirculationfeature is upstream, prior to the inflow air reaching the HEM.Recirculated outflow will have a relative high moisture content and alower carbon dioxide concentration than ambient air, in most cases. Themoisture management system also incorporates a scrubber 60, wherein thescrubber media absorbs moisture from the air inflow. Scrubber mediaworks more effectively when properly hydrated. In addition, the absorbedmoisture in the scrubber media may be periodically desorbed and passedinto the electrochemical cell chamber 120, and subsequently through therest of the moisture management system. The moisture management systemfurther comprises an inflow bypass conduit 75 and valve 76. The controlsystem 102, comprising a microprocessor 106 may open and close valves,including the inflow bypass valve and or a recirculation valve 72 toefficiently operate the system and conserve moisture. For example, thescrubber may be detached and the controller may divert inflow airthrough the bypass conduit to the inflow port 65 of the cell chamber120.

It will be apparent to those skilled in the art that variousmodifications, combinations and variations can be made in the presentdisclosure without departing from the spirit or scope of the disclosure.Specific embodiments, features and elements described herein may bemodified, and/or combined in any suitable manner. Thus, it is intendedthat the present disclosure cover the modifications, combinations andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An electrochemical cell comprising: a) a cellhousing comprising: i) an air chamber; ii) an air chamber inflow port;iii) an air chamber outlet; iv) an electrolyte chamber for retaining avolume of an electrolyte; v) an oxidant reduction electrode for reducinga gaseous oxidant configured between the air chamber and the electrolytechamber, vi) a fuel electrode; wherein a fuel is reacted at the fuelelectrode and wherein the fuel electrode is positioned apart from theoxidant reduction electrode, thereby defining a gap, and wherein saidelectrolyte is in the gap; b) a scrubber module comprising an enclosurecomprising: i) a scrubber media; ii) a scrubber inlet port configured tocouple with an inlet air outflow port; and iii) a scrubber outlet portconfigured to couple with the air chamber inflow port; wherein thescrubber module is detachably attachable to said cell housing, andwhereby the electrochemical cell operates when the scrubber is removed.2. The electrochemical cell of claim 1, wherein the electrolyte is anionically conductive liquid electrolyte.
 3. The electrochemical cell ofclaim 2, wherein the fuel electrode comprises a metal fuel and isconfigured at least partially within the electrolyte wherein the fuelelectrode is positioned apart from the oxidant reduction electrode,thereby defining a gap, and wherein said ionically conductive liquidelectrolyte is in the gap.
 4. The electrochemical cell of claim 1,wherein a flow of air entering the cell housing through the air chamberinflow port and from the scrubber has less carbon dioxide than a flow ofair entering the scrubber through the outflow port from the cellhousing.
 5. The electrochemical cell of claim 1, wherein the scrubbermedia is irreversible scrubber media.
 6. The electrochemical cell ofclaim 5, wherein the irreversible scrubber media is selected from thegroup of consisting of: soda lime, sodium hydroxide, potassiumhydroxide, and lithium hydroxide, lithium peroxide, calcium oxide,calcium carbonate, serpentinite, magnesium silicate, magnesiumhydroxide, olivine, molecular sieves, amines, and monoethanolamine,and/or derivatives and/or combinations thereof.
 7. The electrochemicalcell of claim 1, wherein the scrubber media comprises a reversiblescrubber media.
 8. The electrochemical cell of claim 7, wherein thereversible scrubber media comprises amine groups.
 9. The electrochemicalcell of claim 1, wherein the scrubber comprises a heating element. 10.The electrochemical cell of claim 9, wherein the heating element is apassive heating element that directs heat from the electrochemical cellto the scrubber media.
 11. The electrochemical cell of claim 9, whereinthe heating element comprises an electric heating element that iscontrolled by a control system comprising a microprocessor.
 12. Theelectrochemical cell of claim 1, wherein the housing comprises ahumidity exchange module comprising: a) a humidity exchange membraneconfigured between the inlet airflow to the cell housing and an exhaustairflow received from the air chamber; wherein the humidity exchangemembrane comprises an inflow side exposed to the inlet airflow and anoutflow side exposed to the exhaust airflow; and wherein the exhaustairflow comprises moisture and wherein said moisture is transferredthrough said humidity exchange membrane to the inlet airflow.
 13. Theelectrochemical cell of claim 12, wherein the humidity exchange membranecomprises an ionically conductive polymer.
 14. The electrochemical cellof claim 12, wherein the humidity exchange membrane comprises aperfluorosulfonic acid polymer.
 15. The electrochemical cell of claim12, wherein the inlet airflow flows into the scrubber module afterpassing through the humidity exchange module.
 16. The electrochemicalcell of claim 1, further comprising a recirculation feature thattransfers a portion of exhaust airflow to the inlet airflow, whereby atleast a portion of an exhaust airflow from said air chamber istransferred through said recirculation feature into the inlet airflow.17. The electrochemical cell of claim 12, further comprising arecirculation feature that transfers a portion of exhaust airflow to theinlet airflow. whereby at least a portion of an exhaust airflow fromsaid air chamber is transferred through said recirculation feature intothe inlet airflow.
 18. The electrochemical cell of claim 17, wherein therecirculation feature is a valve and wherein the valve is controlled bythe control system.
 19. The electrochemical cell of claim 17, whereinthe recirculation feature is a baffle and wherein the baffle ispassively controlled by a pressure differential between the exhaustairflow and the inlet airflow.
 20. The electrochemical cell of claim 17,wherein recirculation feature is configured upstream of the humidityexchange membrane module, wherein a portion of the exhaust airflow isrecirculated into the inlet airflow after passing through the humidityexchange module.
 21. The electrochemical cell of claim 12, comprising anairflow device configured to expel exhaust airflow from the cellhousing; wherein the airflow device creates a reduced pressure withinthe cell housing that draws the inlet airflow into the cell housing,through the inflow side of the humidity exchange membrane module,through the scrubber, through the air chamber and through the outflowside of the humidity exchange membrane module.
 22. The electrochemicalcell of claim 21, wherein the reduced pressure within the cell housingwill draw a flow of ambient airflow through the inflow port to thescrubber when the scrubber is detached from the electrochemical cell;whereby the electrochemical cell operates with the scrubber removed. 23.The electrochemical cell of claim 1, further comprising an inflow bypassvalve and inflow bypass conduit, wherein the inflow bypass conduitdiverts inlet airflow to the cell chamber without passing through thescrubber.
 24. The electrochemical cell of claim 1, wherein the inflowbypass valve is controlled by the control system.
 25. Theelectrochemical cell of claim 1, further comprising a bypass adapterthat comprises a conduit that couples the outflow port to the inflowport, wherein the bypass adapter diverts inlet airflow to the cellchamber without passing through the scrubber.
 26. The electrochemicalcell of claim 1, further comprising a heating element that heats thescrubber media.
 27. An electrochemical cell comprising: a) a cellhousing comprising: i) an air chamber; ii) an air chamber inflow port;iii) an air chamber outlet; iv) an electrolyte chamber for retaining avolume of an electrolyte; v) an oxidant reduction electrode for reducinga gaseous oxidant configured between the air chamber and the electrolytechamber, vi) a fuel electrode; wherein a fuel is reacted at the fuelelectrode and wherein the fuel electrode is positioned apart from theoxidant reduction electrode, thereby defining a gap, and wherein saidelectrolyte is in the gap; b) a scrubber module comprising an enclosurecomprising: i) a scrubber media; ii) a scrubber inlet port configured tocouple with an inlet air outflow port; and iii) a scrubber outlet portconfigured to couple with the air chamber inflow port; wherein thescrubber module is detachably attachable to said cell housing, andwhereby the electrochemical cell operates when the scrubber is removed;c) a humidity exchange module comprising: i) humidity exchange membraneconfigured between the inlet airflow to the cell housing and an exhaustairflow received from the air chamber; wherein the humidity exchangemembrane comprises an inflow side exposed to the inlet airflow and anoutflow side exposed to the exhaust airflow; and wherein the exhaustairflow comprises moisture and wherein said moisture is transferredthrough said humidity exchange membrane to the inlet airflow; d) arecirculation feature that transfers a portion of exhaust airflow to theinlet airflow, whereby at least a portion of an exhaust airflow fromsaid air chamber is transferred through said recirculation feature intothe inlet airflow.
 28. A method of conserving moisture within anelectrochemical cell comprising the steps of: a) Providing anelectrochemical cell comprising: i) a cell housing comprising: an airchamber; an air chamber air inlet; an air chamber air outlet; anelectrolyte chamber for retaining a volume of an ionically conductiveliquid electrolyte; an oxidant reduction electrode for reducing agaseous oxidant configured between the air chamber and the electrolytechamber, a fuel electrode comprising a metal fuel and configured atleast partially within the electrolyte chamber; wherein the fuelelectrode is positioned apart from the oxidant reduction electrode,thereby defining a gap, and wherein said ionically conductive liquidelectrolyte is in the gap; ii) a scrubber module comprising an enclosurecomprising: a scrubber media; a scrubber inlet port; and a scrubberoutlet port; wherein the scrubber module is detachably attachable tosaid cell housing, and whereby the electrochemical cell operates whenthe scrubber is removed; iii) a humidity exchange module comprising:humidity exchange membrane configured between the inlet airflow to thecell housing and an exhaust airflow received from the air chamber;wherein the humidity exchange membrane comprises an inflow side exposedto the inlet airflow and an outflow side exposed to the exhaust airflow;and wherein the exhaust airflow comprises moisture and wherein saidmoisture is transferred through said humidity exchange membrane to theinlet airflow; iv) a recirculation feature comprising a recirculationvalve, wherein the recirculation feature is configured to transfer aportion of exhaust airflow to the inlet airflow, whereby at least aportion of an exhaust airflow from said air chamber is transferredthrough said recirculation feature into the inlet airflow; v) an airflowdevice configured to expel exhaust airflow from the cell housing; b)operating the airflow device to create a reduced pressure within thecell housing that draws the inlet airflow into the cell housing, throughthe inflow side of the humidity exchange membrane module, through thescrubber, through the air chamber and through the outflow side of thehumidity exchange membrane module; c) opening the recirculation valve towhereby at least a portion of an exhaust airflow from said air chamberis transferred through said recirculation feature into the inletairflow.
 29. The method of conserving moisture within an electrochemicalcell of claim 28, wherein recirculation feature is configured upstreamof the humidity exchange membrane module, wherein a portion of theexhaust airflow is recirculated into the inlet airflow after passingthrough the humidity exchange module.
 30. The method of conservingmoisture within an electrochemical cell of claim 28, wherein thescrubber comprises a heating element and wherein absorbed moisture onthe scrubber media is driven into the electrochemical cell housing bythe inlet airflow through scrubber and heating of the scrubber media bythe heating element.
 31. The method of conserving moisture within anelectrochemical cell of claim 30, further comprising the step of:running the airflow device when the electrochemical cell is not activelyproducing electricity to absorb moisture from the environment on thescrubber media; and subsequently, driving said absorbed moisture fromthe scrubber media by the inlet airflow through scrubber and heating ofthe scrubber media by the heating element.